The present invention concerns a novel technique for monitoring the link between a pair of stations in a frame-based network by means of decompression of frames transmitted in a compressed state between the stations. It is customary to transmit frames which are compressed according to a compression algorithm which requires the maintenance of a compression history by the two stations at the ends of the link. The monitoring device or probe maintains, according to the invention, a compression history which, for a given direction of transmission of frames, corresponds to the compression history maintained by the receiver of those frames.